访问 OnValueUpdated 快照内的数据

Question

我想访问更改后的数据。快照后（来自 Firebase 实时数据库） 这是代码：

exports.requestListener = onValueUpdated('/ride_info/{pushId}', async (change,context) => {
    //const data = snapshot.val; // Use snapshot.val() to get the data
       // Access `before` and `after` snapshots

       // Log the change object to debug the structure
        console.log('Change Object:', JSON.stringify(change, null, 2));
        
        const beforeSnapshot = change.before;
        const afterSnapshot = change.after;

 const before = change.before.val(); // Get the data before the update
        const after = change.after.val(); 
     
    const id_customer = after.customerId;
     console.log(id_customer);
    const id_driver = after.driverId;
    const id_ride = context.params.pushId;

这是变更对象的结构：

更改对象：

{
    "source": "//firebasedatabase.googleapis.com/projects/_/locations/europe-west1/instances/*********",
    "time": "2024-05-24T06:49:57.561Z",
    "id": "*******",
    "ref": "ride_info/NydMFHRB89yV1ODcc1z",
    "instance": "********",
    "specversion": "1.0",
    "subject": "refs/ride_info/NydMFHRB89yV1ODcc1z",
    "location": "europe-west1",
    "type": "google.firebase.database.ref.v1.updated",
    "data": {
        "before": {
            "SelectMinutes": 0,
            "SelectedHour": 0,
            "calculated_distance": 0,
            "calculated_duration": 0,
            "creation_timestamp": 1716533396799,
            "customerId": "79axhZrQzVcIbl3I6J2i6PJ40oQ2",
            "ended": false,
            "pickup": {
                "lat": 48.8578763,
                "lng": 2.4061916,
                "name": "Paris, Square de la Salamandre"
            },
            "price_calculated": false,
            "rating": -1,
            "rating_calculated": false,
            "service": "type_1",
            "state": 0,
            "validated": false
        },
        "after": {
            "SelectMinutes": 0,
            "SelectedHour": 0,
            "calculated_distance": 0.008233495056629181,
            "calculated_duration": 0,
            "creation_timestamp": 1716533396799,
            "customerId": "79axhZrQzVcIbl3I6J2i6PJ40oQ2",
            "ended": false,
            "pickup": {
                "lat": 48.8578763,
                "lng": 2.4061916,
                "name": "Paris, Square de la Salamandre"
            },
            "price_calculated": false,
            "rating": -1,
            "rating_calculated": false,
            "service": "type_1",
            "state": 0,
            "validated": false,
            "calculated_Price": 36,
            "destination": {
                "lng": 2.4061738,
                "lat": 48.8578032
            }
        }
    },
    "traceparent": "****************",
    "firebaseDatabaseHost": "europe-west1.firebasedatabase.app",
    "params": {
        "pushId": "NydMFHRB89yV1ODcc1z"
    }
}

我无法访问快照后的值：我得到了

TypeError：无法在此行读取未定义的属性（读取“val”） const after = change.after.val();

Answer 1

您在代码中混合了第一代和第二代 Cloud Functions 的语法，这是行不通的。在第二代 Cloud Functions 中，您可以使用以下方式读取之前的值：

exports makeUppercase = onValueWritten("/messages/{pushId}/original", (event) => {
    // Only edit data when it is first created.
    if (event.data.before.exists()) {
      return null;
    }
    // Exit when the data is deleted.
    if (!event.data.after.exists()) {
      return null;
    }
    // Grab the current value of what was written to the Realtime Database.
    const original = event.data.after.val();
    console.log('Uppercasing', event.params.pushId, original);
    const uppercase = original.toUpperCase();
    // You must return a Promise when performing asynchronous tasks inside a Functions such as
    // writing to the Firebase Realtime Database.
    // Setting an "uppercase" sibling in the Realtime Database returns a Promise.
    return event.data.after.ref.parent.child('uppercase').set(uppercase);
  });